1. Field of the Invention
The present invention relates generally to data communications.
2. Related Art
A known type of data communication device is a small form factor pluggable (SFP) module. Typically, the SFP module plugs into an interface slot in a circuit board populated with other communication devices used in an Ethernet-based system, for example. The SFP module includes a second serial interface, interconnected with the circuit board slot, and a first serial interface, coupled to a serial link, such as a copper or fiber link, for communicating with remote link partners. The SFP module transfers symbols between its first and second interfaces. The second serial interface may include portions of a Serial Gigabit Media Independent Interface (SGMII) that are compatible with an industry standard SerDes interface. The serial link, coupled with the first serial interface, may be a 10/100/1000 Base-T copper link, or a fiber link, for example.
The SFP module is considered a third generation communication module because it evolved from precursor first and second generation modules. The first generation module is often referred to as a proprietary custom module or device, and includes interfaces similar to the first and second interfaces of the SFP module, described above. The second generation module is referred to as a Gigabit Interface Converter (GBIC) module. Typically, the second interface of the GBIC module is an industry standard GBIC interface compatible with the SerDes interface, and the first interface may be configured according to 10, 100, 1000Base-T copper, 1000Base-SX/LX fiber, or 100Base-FX fiber, for example. The SFP module is similar to the GBIC module, but smaller. For convenience, the first, second and third generation modules described above are each generally referred to herein as a “link module.”
Typically, a media access control (MAC) device, such as an Ethernet Switch/MAC, is also mounted onto the circuit board supporting the SFP module (i.e., the link module) described above. In one configuration, the MAC device includes a serial interface compatible with and connected directly to the second serial interface of the link module. In another configuration, the MAC device includes a parallel interface, such as a Reduced Gigabit Media Independent Interface (RGMII), instead of the MAC serial interface. The MAC parallel interface can not be connected directly to the second serial interface of the link module because these two interfaces are incompatible. Therefore, there is a need for an interface arrangement that interconnects the MAC parallel interface and the second serial interface of the link module, and thus enables the MAC and link modules to communicate with one another.
The MAC parallel interface and the serial link coupled with the link module (e.g., the SFP module) may operate at the same or different symbol rates. Therefore, it is desirable that the above mentioned interface arrangement be able to facilitate symbol transfers between the MAC device and the Link module, and over the serial link, when the symbol rates are the same as one another and when the symbol rates are different from one another.